The present invention relates to a device for heat treatment of continuous material webs by blowing of hot steam.
A drying in pure hot steam is very efficient, since it is not necessary to heat any air coming from outside. This is described in the book "Drying and drying processes" of K. Kroll, Springer-verlag 1959, page 37. Additional factors also contribute to the efficiency of this matter, such as the fact that waste air cleaning is dispensed with since no waste is produced. The latent heat contained in the waste steam can be recovered relatively simple by condensation. Because of the low density of the steam, the consumption of electrical energy for recirculation of the drying medium is approximately 1/3 lower than in driers operating with hot air. A further advantage which is especially important for drying textiles is described in the above mentioned book on page 177. The heat steam drying improves the material web, imparts a good feel to it, and allows the colors to appear fresh and clear. The hot steam drying can be provided not only for material webs of natural fibers, but also for such material webs which are produced from synthetic fibers. They can be treated with temperatures of 100-300.degree. C.
The German document DE 35 11 950 discloses a heat steam dryer, from which the present invention is derived. The material web is brought for example by tensioning chains through a slot formed in the bottom of the housing, and can be guided in and out of the housing through the slot. The slot is provided with special seals.
As disclosed in the above mentioned book on page 103, it is not very simple in the practice to form a heat steam dryer for a continuous operation, for example for fabric webs, so tight that no air can penetrate into it. The problems arise not only with the slot for the material web-guiding tensioning chain, but also for example for conduits which extend through the housing wall, doors, or passages for a sieve.